1. Field of the Invention
This invention relates to a lathe comprising a saddle, which is movable along a line which is parallel to a main axis that is defined by the headstock and the tailstock, and two juxtaposed cross slides, which are provided with toolholders and are slidably mounted on the saddle.
2. Description of the Prior Art
To permit the use of lathe tools as well as of boring, drilling and milling tools for machining a workpiece without a need for rechucking the workpiece, it is known to mount on a saddle of a lathe a turret, which is movable by a cross slide into engagement with the workpiece and which carries a tool head provided with a tool spindle, which in the operating position of the tool head is adapted to be coupled to a drive that is mounted on the cross slide. A boring or drilling or milling tool gripped by the toolholder of the tool head may also be used to machine a workpiece which has been chucked in the lathe. In that case, the orientation of the tool will be determined by its position relative to the turret so that separate tool heads are required for a machining in the direction of the main axis defined by the headstock and the tailstock and for a machining at right angles to that main axis. This requirement involves a considerable expenditure. Besides, the mounting of the tool heads for the milling, boring and drilling tools on a turret involves difficulties as regards an adequate support of the tool and as regards the ensuring of a machining to close tolerances. Moreover, the turret may interfere with the use of the boring, drilling and milling tools if the workpiece or the tailstock restricts the movement to be performed by the turret in order to engage the tool with the workpiece.
In an attempt to avoid said disadvantages a lathe has been proposed in which one tool head is provided with a tool spindle for carrying a boring or drilling or milling tool and with a toolholder for a lathe tool. Because the axes of the toolholders for the boring or drilling and milling tool, on the one hand, and for the lathe tool, on the other hand, are at right angles to each other and the tool head is pivoted to the cross slide carrying the tool head on an axis which bisects the angle between the axes of the toolholders and is inclined 45.degree. from the main axis of the lathe, the axes of the tool holder can selectively be adjusted to be parallel and at right angles to the main axis by a rotation of the tool head so that the range of the machining operations which can be performed is correspondingly increased. On the other hand, no tool magazine for changing tools is available near the machining station so that the down times for a change of tools are considerably increased, even if a suitable tool-changing device is provided on the side of the lathe. This long down time is due to the fact that the saddle carrying the tool head must be moved out of the machining station to the tool-changing device.
It is also known from German Patent Specification No. 353,819 to mount two cross slides on the saddle of a lathe and to provide a drive by which the two cross slides can be moved only equal amounts in opposite directions. That adjustment by equal amount in opposite directions involves such a great restriction of the free space which is available for moving the tool into engagement with the workpiece that an efficient use of lathe tools, on the one hand, and of milling, boring and drilling tools, on the other hand, is not possible.